Add constructors to all the event classes.

client/html/src/ErrorEventWrappingImplementation.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// WARNING: Do not edit - generated code.
-
 class ErrorEventWrappingImplementation extends EventWrappingImplementation implements ErrorEvent {
   ErrorEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
 
+  factory ErrorEventWrappingImplementation(String type, String message,
+      String filename, int lineNo, [bool canBubble = false,
+      bool cancelable = false]) {
+    var e = dom.document.createEvent("ErrorEvent");
+    e.initErrorEvent(type, canBubble, cancelable, message, filename, lineNo);
+    return LevelDom.wrapErrorEvent(e);
+  }
+
   String get filename() { return _ptr.filename; }
 
   int get lineno() { return _ptr.lineno; }
 
   String get message() { return _ptr.message; }
-
-  void initErrorEvent(String typeArg, bool canBubbleArg, bool cancelableArg, String messageArg, String filenameArg, int linenoArg) {
-    _ptr.initErrorEvent(typeArg, canBubbleArg, cancelableArg, messageArg, filenameArg, linenoArg);
-    return;
-  }
 }